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77 I added .75 ounces of lead to the free, f end 6f the throw bar to'helplbalance-'3 the tunnel curtain's weight. Without this' 1 weight,_the curtain traveled too fast 2, 4 going tiown and too slow going up. Next, I connected the motor to a temporary 12,V DC.power supply to test the operation. Blower house I used a great deal of "modeler's license" when I built the blower house' and air intake. The main walls of the blowerhouse were made from A. I. M. tapered abutment wings while the remainder of thie surrounding structures were simple, quick, and fun miniscratchbuilding proJects. I needed a souice of power for the .4 tunnel's massivib::air blowers: If you , think your electric bill'.was high last summer, imagin6 what BN's Cascade Tunnel must suck up yearly! Similar to the BN operation, th254MKQ substation near the blower house. I built the power substation from a Con-Cor kit, but'due to space limitations:I used only half of the kit. By the way, a neat method of repre- senting those glass insulators found on Power poles and transformers is to first paint the insulators white and then apply one or two coats of colored-glass stain available at most craft stores. The result is shiny, glassy-looking insulators. The fail-safe device Figure 3 shows how the electrical system is connected. I used two Circuitron opticalldetector blocks; one for triggering the tunnel-curtain operation and the other for triggering the signal at the face of the portal. The signal-detection block overlaps the tunnel-curtain detection block. The two-aspect signal at the tunnel portal provide-s important information to the train crew. The signal is normally · red when the curtain- is down and will only display green if the curtain is fully up and no other trains are jn the signaldetection block. This Interlocking feature between the curtain position and the signal-detection block was easily accomplished by routing the power through relays. The fail-safe feature uses the posi- tion of the curtain to either apply or cut power to a short section of isolated rail on either side of the portal. When the curtain is up, a smalllever switch closes and provides power to the track. If for some reason the curtain fails to open completely, the locomotive will stop on the dead section of · track before it hits the curtain. I soldered a 1,000-ohm, 1-watt resistor to the Switchmaster motor in series for .7 - 3. , U % ....4 el""49: -4t realistic curtain operating speed. You may need to vary the value of this resistor for your particular application. If your curtain travels too slowly, try a slightly lower value resistor and vice versa. It works! I had fun designing and building the tunnel curtain, but the real fun lies in ./ =1'· -'f " r >....' r --42 ·042ZZ.. . F . a 41,·, / J --, 4 li - 9 4 4.-,29$••. f:t, S. f. 1,54 ':• hU# " 4 b.5. :pr 1' .'4.14, • .A + Here's the completed curtain in its closed position. The blower house for tunnel ventilation is just for show, but your visitors don't have to know that. the operation. I especially enjoy watching first-time visitors when they spot the closed tunnel curtain with a train approaching. To their relief and amazement, and my pride and amusement, the curtain slowly rises just before the train arrives'. At the same time, the red signal winks to green. It's a bit of fun that never gets old. 0 MODEL RAILROADER 79 0 t. , , - 4 : P 1 1 1 -'r 1.r H-\., 11 ri 1, - /0 foq,\ 1 34/ has a power - ' - b " ,. / '' 1 10« 1 .-I E' ..6 11, 1 .2 * 3 1 i c :119• 036 1*1ek., Mt*.B# 1 *33, 1 1 f * p: '>